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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="circular_buffer.implementation"></a><a class="link" href="implementation.html" title="Implementation">Implementation </a>
</h2></div></div></div>
<p>
      The following paragraphs describe issues that had to be considered during the
      implementation of the circular_buffer:
    </p>
<h4>
<a name="circular_buffer.implementation.h0"></a>
      <span class="phrase"><a name="circular_buffer.implementation.thread_safety"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.thread_safety">Thread-Safety</a>
    </h4>
<p>
      The thread-safety of the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      is the same as the thread-safety of containers in most STL implementations.
      This means the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      is not fully thread-safe. The thread-safety is guaranteed only in the sense
      that simultaneous accesses to distinct instances of the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      are safe, and simultaneous read accesses to a shared <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      are safe.
    </p>
<p>
      If multiple threads access a single <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>,
      and at least one of the threads may potentially write, then the user is responsible
      for ensuring mutual exclusion between the threads during the container accesses.
      The mutual exclusion between the threads can be achieved by wrapping operations
      of the underlying <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      with a lock acquisition and release. (See the Bounded Buffer example code at
      <a href="../../../libs/circular_buffer/example/circular_buffer_bound_example.cpp" target="_top">circular_buffer_bound_example.cpp</a>)
    </p>
<h4>
<a name="circular_buffer.implementation.h1"></a>
      <span class="phrase"><a name="circular_buffer.implementation.overwrite_operation"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.overwrite_operation">Overwrite
      Operation</a>
    </h4>
<p>
      Overwrite operation occurs when an element is inserted into a full <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> - the old element
      is being overwritten by the new one. There was a discussion what exactly "overwriting
      of an element" means during the formal review. It may be either a destruction
      of the original element and a consequent inplace construction of a new element
      or it may be an assignment of a new element into an old one. The <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> implements assignment
      because it is more effective.
    </p>
<p>
      From the point of business logic of a stored element, the destruction/construction
      operation and assignment usually mean the same. However, in very rare cases
      (if in any) they may differ. If there is a requirement for elements to be destructed/constructed
      instead of being assigned, consider implementing a wrapper of the element which
      would implement the assign operator, and store the wrappers instead. It is
      necessary to note that storing such wrappers has a drawback. The destruction/construction
      will be invoked on every assignment of the wrapper - not only when a wrapper
      is being overwritten (when the buffer is full) but also when the stored wrappers
      are being shifted (e.g. as a result of insertion into the middle of container).
    </p>
<h4>
<a name="circular_buffer.implementation.h2"></a>
      <span class="phrase"><a name="circular_buffer.implementation.writing_to_a_full_buffer"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.writing_to_a_full_buffer">Writing to
      a Full Buffer</a>
    </h4>
<p>
      There are several options how to cope if a data source produces more data than
      can fit in the fixed-sized buffer:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          Inform the data source to wait until there is room in the buffer (e.g.
          by throwing an overflow exception).
        </li>
<li class="listitem">
          If the oldest data is the most important, ignore new data from the source
          until there is room in the buffer again.
        </li>
<li class="listitem">
          If the latest data is the most important, write over the oldest data.
        </li>
<li class="listitem">
          Let the producer to be responsible for checking the size of the buffer
          prior writing into it.
        </li>
</ul></div>
<p>
      It is apparent that the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      implements the third option. But it may be less apparent it does not implement
      any other option - especially the first two. One can get an impression that
      the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> should
      implement first three options and offer a mechanism of choosing among them.
      This impression is wrong.
    </p>
<p>
      The <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> was
      designed and optimized to be circular (which means overwriting the oldest data
      when full). If such a controlling mechanism had been enabled, it would just
      complicate the matters and the usage of the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      would be probably less straightforward.
    </p>
<p>
      Moreover, the first two options (and the fourth option as well) do not require
      the buffer to be circular at all. If there is a need for the first or second
      option, consider implementing an adaptor of e.g. std::vector. In this case
      the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> is
      not suitable for adapting, because, contrary to std::vector, it bears an overhead
      for its circular behaviour.
    </p>
<h4>
<a name="circular_buffer.implementation.h3"></a>
      <span class="phrase"><a name="circular_buffer.implementation.reading_removing_from_an_empty_b"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.reading_removing_from_an_empty_b">Reading/Removing
      from an Empty Buffer</a>
    </h4>
<p>
      When reading or removing an element from an empty buffer, the buffer should
      be able to notify the data consumer (e.g. by throwing underflow exception)
      that there are no elements stored in it. The <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      does not implement such a behaviour for two reasons:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          It would introduce a performance overhead.
        </li>
<li class="listitem">
          No other std container implements it this way.
        </li>
</ul></div>
<p>
      It is considered to be a bug to read or remove an element (e.g. by calling
      <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html#doxygen.boost_circular_buffer_c___reference.classboost_1_1circular__buffer_1a0d5fdeabeb352f47d1f7bb1ea8d9819f">front()</a></code> or
      <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html#doxygen.boost_circular_buffer_c___reference.classboost_1_1circular__buffer_1adf0da00cb501bea75afbbfab9f546a07">pop_back()</a></code>)
      from an empty std container and from an empty <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      as well. The data consumer has to test if the container is not empty before
      reading/removing from it by testing <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html#doxygen.boost_circular_buffer_c___reference.classboost_1_1circular__buffer_1a12c932f15d9028d99dd87ae890e60088">empty()</a></code>.
      However, when reading from the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>,
      there is an option to rely on the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html#doxygen.boost_circular_buffer_c___reference.classboost_1_1circular__buffer_1acd84838cb4fffb6c113fd0297e502edc">at()</a></code>
      method which throws an exception when the index is out of range.
    </p>
<h4>
<a name="circular_buffer.implementation.h4"></a>
      <span class="phrase"><a name="circular_buffer.implementation.iterator_invalidation"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.iterator_invalidation">Iterator
      Invalidation</a>
    </h4>
<p>
      An iterator is usually considered to be invalidated if an element, the iterator
      pointed to, had been removed or overwritten by an another element. This definition
      is enforced by the Debug Support and is documented for every method. However,
      some applications utilizing <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      may require less strict definition: an iterator is invalid only if it points
      to an uninitialized memory.
    </p>
<p>
      Consider following example:
    </p>
<pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">BOOST_CB_ENABLE_DEBUG</span> <span class="number">0</span> <span class="comment">// The Debug Support has to be disabled, otherwise the code produces a runtime error.</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">circular_buffer</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">assert</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">assert</span><span class="special">.</span><span class="identifier">h</span><span class="special">&gt;</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="comment">/*argc*/</span><span class="special">,</span> <span class="keyword">char</span><span class="special">*</span> <span class="comment">/*argv*/</span><span class="special">[])</span>
<span class="special">{</span>

  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">circular_buffer</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">cb</span><span class="special">(</span><span class="number">3</span><span class="special">);</span>

  <span class="identifier">cb</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">1</span><span class="special">);</span>
  <span class="identifier">cb</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">2</span><span class="special">);</span>
  <span class="identifier">cb</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">3</span><span class="special">);</span>

  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">circular_buffer</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;::</span><span class="identifier">iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">cb</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span>

  <span class="identifier">assert</span><span class="special">(*</span><span class="identifier">it</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span>

  <span class="identifier">cb</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">4</span><span class="special">);</span>

  <span class="identifier">assert</span><span class="special">(*</span><span class="identifier">it</span> <span class="special">==</span> <span class="number">4</span><span class="special">);</span> <span class="comment">// The iterator still points to the initialized memory.</span>

  <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
      The iterator does not point to the original element any more (and is considered
      to be invalid from the "strict" point of view) but it still points
      to the same valid place in the memory. This "soft" definition of
      iterator invalidation is supported by the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      but should be considered as an implementation detail rather than a full-fledged
      feature. The rules when the iterator is still valid can be inferred from the
      code in <a href="../../../libs/circular_buffer/test/soft_iterator_invalidation.cpp" target="_top">soft_iterator_invalidation.cpp</a>.
    </p>
<h4>
<a name="circular_buffer.implementation.h5"></a>
      <span class="phrase"><a name="circular_buffer.implementation.move_emulation_and_rvalues"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.move_emulation_and_rvalues">Move emulation
      and rvalues</a>
    </h4>
<p>
      Since Boost 1.54.0 support for move semantics was implemented using the <a href="../../../libs/move/index.html" target="_top">Boost.Move</a> library. If rvalue references
      are available <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      will use them, but if not it uses a close, but imperfect emulation. On such
      compilers:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          Non-copyable objects can be stored in the containers. They can be constructed
          in place using <code class="computeroutput"><span class="identifier">emplace</span></code>,
          or if they support Boost.Move, moved into place.
        </li>
<li class="listitem">
          The containers themselves are not movable.
        </li>
<li class="listitem">
          Argument forwarding is not perfect.
        </li>
</ul></div>
<p>
      <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> will use
      rvalues and move emulations for value types only if move constructor and move
      assignment operator of the value type do not throw; or if the value type has
      no copy constructor.
    </p>
<p>
      Some methods won't use move constructor for the value type at all, if the constructor
      throws. This is required for data consistency and avoidance of situations,
      when aftrer an exception <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      contains moved away objects along with the good ones.
    </p>
<p>
      See documentation for <a href="../../../libs/type_traits/doc/html/boost_typetraits/reference/is_copy_constructible.html" target="_top"><code class="computeroutput"><span class="identifier">is_copy_constructible</span></code></a>, <a href="../../../libs/type_traits/doc/html/boost_typetraits/reference/is_nothrow_move_assignable.html" target="_top"><code class="computeroutput"><span class="identifier">is_nothrow_move_assignable</span></code></a> and <a href="../../../libs/type_traits/doc/html/boost_typetraits/reference/is_nothrow_move_constructible.html" target="_top"><code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span></code></a> type
      triats. There you'll find information about how to make constructor of class
      noexcept and how to make a non-copyable class in C++03 and C++98.
    </p>
<p>
      Performance of <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      will <span class="bold"><strong>greatly improve</strong></span> if value type has noexcept
      move constructor and noexcept move assignment.
    </p>
<h4>
<a name="circular_buffer.implementation.h6"></a>
      <span class="phrase"><a name="circular_buffer.implementation.exceptions_of_move_if_noexcept_t"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.exceptions_of_move_if_noexcept_t">Exceptions
      of move_if_noexcept(T&amp;)</a>
    </h4>
<p>
      Reference documentation of the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      contains notes like "Throws: See Exceptions of <code class="computeroutput"><span class="identifier">move_if_noexcept</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;)</span></code>".
      That note means the following: <code class="computeroutput"><span class="identifier">move_if_noexcept</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;</span>
      <span class="identifier">value</span><span class="special">)</span></code>
      does not throws exceptions at all, but it returns <code class="computeroutput"><span class="identifier">value</span></code>
      as rvalue reference only if class <code class="computeroutput"><span class="identifier">T</span></code>
      have noexcept move constructor and noexcept move assignment operator; or if
      it has no copy constructor. Otherwise <code class="computeroutput"><span class="identifier">move_if_noexcept</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;</span>
      <span class="identifier">value</span><span class="special">)</span></code>
      returns <code class="computeroutput"><span class="identifier">value</span></code> as const reference.
    </p>
<p>
      This leads us to the following situation:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          If <code class="computeroutput"><span class="identifier">value</span></code> has a noexcept
          move constructor and noexcept move assignment operator, then no exceptions
          will be thrown at all.
        </li>
<li class="listitem">
          If <code class="computeroutput"><span class="identifier">value</span></code> has a throwing
          move constructor and some copy constructor, then method may throw exceptions
          of copy constructor.
        </li>
<li class="listitem">
          If <code class="computeroutput"><span class="identifier">value</span></code> has no copy constructor,
          then method may throw exceptions of move constructor.
        </li>
</ul></div>
<p>
      <code class="computeroutput"><span class="identifier">move_if_noexcept</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;)</span></code> uses
      <a href="../../../libs/move/index.html" target="_top">Boost.Move</a>, <a href="../../../libs/type_traits/doc/html/boost_typetraits/reference/is_copy_constructible.html" target="_top"><code class="computeroutput"><span class="identifier">is_copy_constructible</span></code></a>, <a href="../../../libs/type_traits/doc/html/boost_typetraits/reference/is_nothrow_move_assignable.html" target="_top"><code class="computeroutput"><span class="identifier">is_nothrow_move_assignable</span></code></a> and <a href="../../../libs/type_traits/doc/html/boost_typetraits/reference/is_nothrow_move_constructible.html" target="_top"><code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span></code></a> type
      triats.
    </p>
<h4>
<a name="circular_buffer.implementation.h7"></a>
      <span class="phrase"><a name="circular_buffer.implementation.caveats"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.caveats">Caveats</a>
    </h4>
<p>
      The <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> should
      not be used for storing pointers to dynamically allocated objects. When a circular
      buffer becomes full, further insertion will overwrite the stored pointers -
      resulting in a <span class="bold"><strong>memory leak</strong></span>. One recommend
      alternative is the use of smart pointers, for example <a href="http://www.boost.org/doc/libs/1_53_0/libs/smart_ptr/smart_ptr.htm" target="_top">Boost
      Smart pointers</a>.
    </p>
<p>
      <a href="http://en.wikipedia.org/wiki/Std::auto_ptr" target="_top">std::auto_ptr</a>
    </p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../doc/src/images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
        Any container of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">auto_ptr</span></code> is considered particularly hazardous.
      </p></td></tr>
</table></div>
<div class="tip"><table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../doc/src/images/tip.png"></td>
<th align="left">Tip</th>
</tr>
<tr><td align="left" valign="top"><p>
        Never create a circular buffer of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">auto_ptr</span></code>.
        Refer to Scott Meyers' excellent book Effective STL for a detailed discussion.
        (Meyers S., Effective STL: 50 Specific Ways to Improve Your Use of the Standard
        Template Library. Addison-Wesley, 2001.)
      </p></td></tr>
</table></div>
<p>
      While internals of a <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      are circular, <span class="bold"><strong>iterators are not</strong></span>. Iterators
      of a <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> are
      only valid for the range <code class="computeroutput"><span class="special">\[</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">end</span><span class="special">()\]</span></code>,
      so for example: iterators <code class="computeroutput"><span class="special">(</span><span class="identifier">begin</span><span class="special">()</span> <span class="special">-</span> <span class="number">1</span><span class="special">)</span></code> and <code class="computeroutput"><span class="special">(</span><span class="identifier">end</span><span class="special">()</span> <span class="special">+</span>
      <span class="number">1</span><span class="special">)</span></code> are
      both invalid.
    </p>
<h4>
<a name="circular_buffer.implementation.h8"></a>
      <span class="phrase"><a name="circular_buffer.implementation.debug_support"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.debug_support">Debug
      Support</a>
    </h4>
<p>
      In order to help a programmer to avoid and find common bugs, the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> can be enabled to
      provide a kind of debug support.
    </p>
<p>
      When the debugging functionality is enabled, the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      maintains a list of valid iterators. As soon as any element gets destroyed
      all iterators pointing to this element are removed from this list and explicitly
      invalidated (an invalidation flag is set). The debug support also consists
      of many assertions (<code class="computeroutput"><span class="identifier">BOOST_ASSERT</span></code>
      macros) which ensure the <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      and its iterators are used in the correct manner at runtime. In case an invalid
      iterator is used, the assertion will report an error. The connection of explicit
      iterator invalidation and assertions makes a very robust debug technique which
      catches most of the errors.
    </p>
<p>
      Moreover, the uninitialized memory allocated by <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      is filled with the value <code class="computeroutput"><span class="number">0xcc</span></code> in
      the debug mode. When debugging the code, this can help the programmer to recognize
      the initialized memory from the uninitialized. For details refer the source
      code <a href="../../../boost/circular_buffer/debug.hpp" target="_top">circular_buffer/debug.hpp</a>.
    </p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../doc/src/images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
        Since the debugging code makes <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
        and its iterators more interconnected, thread safety guarantees of <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> are different when
        debug support is enabled. In addition to the container itself, all iterators
        tracked by the container (including any copies thereof) must be protected
        from concurrent access. In particular, this includes copying, destroying
        or obtaining iterators from the container, even if for read-only access.
      </p></td></tr>
</table></div>
<p>
      The debug support is disabled by default. To enable it, one has to define
      <code class="computeroutput"><span class="identifier">BOOST_CB_ENABLE_DEBUG</span></code> macro
      with the value of 1 while compiling the code using <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>.
    </p>
<h4>
<a name="circular_buffer.implementation.h9"></a>
      <span class="phrase"><a name="circular_buffer.implementation.compatibility_with_interprocess_"></a></span><a class="link" href="implementation.html#circular_buffer.implementation.compatibility_with_interprocess_">Compatibility
      with Interprocess library</a>
    </h4>
<p>
      The <code class="computeroutput"><a class="link" href="../doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> is
      compatible with the <a href="../../../libs/interprocess/index.html" target="_top">Boost.Interprocess</a>
      library used for interprocess communication. Considering that the circular_buffer's
      debug support relies on 'raw' pointers (which is not permitted by the Interprocess
      library) the code has to compiled with debug support disabled (i.e. with <code class="computeroutput"><span class="identifier">BOOST_CB_ENABLE_DEBUG</span></code> macro not defined or
      defined to 0). Not doing that will cause the compilation to fail.
    </p>
</div>
<div class="copyright-footer">Copyright © 2003-2013 Jan Gaspar<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div>
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